Sources & References
Where our claims come from
Last updated: 10 August 2026
CSS support and best practices shift as browsers ship new engines and the spec evolves. Here's what we cite when a guide makes a claim about syntax, browser support, or performance — and how we test the tools we list.
Reference sources for our guides
Our CSS guides and comparison articles (grid vs. flexbox, custom properties, the:has() selector, and others in the blog) are checked against these authoritative sources rather than written from memory alone:
MDN Web Docs ↗
Property definitions, syntax, and browser-support tables cited across our CSS guides.
W3C / CSS Working Group specs ↗
The formal specifications behind CSS features — what a property is actually defined to do, not just how browsers happen to implement it.
Can I Use ↗
Real-world browser support data, used when a guide makes a claim about which browsers support a given feature.
web.dev (Google) ↗
Performance and best-practice guidance referenced in our optimization and accessibility content.
How we test tools before listing
Every tool submission is opened and used directly, in a current version of Chrome — not evaluated from its marketing page alone. We check that the core functionality it claims actually works, that the site loads and isn't broken, and that the category/tags we assign match what the tool does. Full criteria are on the Editorial Policy page.
When content goes stale
Browser support tables and best-practice guidance change. If you spot a guide citing outdated support data or a superseded technique, use the feedback icons on that page (where present) or contact us directly — corrections to published guides are generally shipped within a few days.